Act as a Senior Solutions Architect. You have been tasked with migrating a 10-year-old monolithic e-commerce platform (written in Java using a monolithic SQL database) to a microservices architecture. The system cannot tolerate more than 5 minutes of downtime. Draft a comprehensive migration plan that includes: 1) A strategy for database decomposition (shared database vs. database per service), 2) The use of the Strangler Fig pattern to incrementally replace functionality, 3) Handling session management across distributed services, and 4) A rollback strategy in case of critical failure during the transition. Explain the trade-offs involved in each decision.